MRI is routinely used in the evaluation and management of patients with failed back surgery syndrome (FBSS). However, its value is unclear in the early detection of signs that can negatively affect that later course of surgical cases. The purpose of the present study is to describe the MR images of early postoperative MRI at 3 days in 30 unselected patients who underwent lumbar microdiscectomy, and to correlate the findings with follow up MRI at 8 weeks and with final outcome. The findings are correlated with literature data. Early postoperative MRI findings were consisting of pseudohernia in 24 patients (80%), annular rent in 23 patients (80%), and other non-specific postoperative findings. On the late MRI the pseudohernia persisted in 12 patients (50%), the annular rent in 4 patients (15%) and asymptomatic pseudo-spondylodiscitis was apparent in 3 patients (10%) as was a case of true spondylodiscitis. Therefore, early postoperative findings have limited value in the management of patients after surgery for lumbar disc herniation, since the images were not correlated with the immediate clinical course after surgery nor with the late radiological and clinical outcome. The evident imaging changes in the early postoperative period after lumbar disc surgery limit the accuracy of the interpretation of MRI examinations.

The aim of our study was to evaluate the contrast-enhanced MR imaging (MRI) findings, in the early postoperative period, in unselected patients undergoing lumbar microdiscectomy (15/16 had total resolution of their symptoms). Contrast-enhanced imaging studies were performed, in all 16 patients of our series, before surgery, and at the third postoperative day and, two months after surgery. Postoperative paraspinal muscles enhancement was present in all patients. In the postoperative period, nerve root enhancement was present in 5/16 patients at the early survey and persisted in one after two months. A pseudohernia depicted as epidural intermediate signal intensity tissue, was seen in 13 patients at the third day MRI, and only in eight after two months. This pseudohernia enhanced peripherally in 8/13 patients and enhanced homogeneously in the remaining five at the first postsurgical examination; in the late MRI the peripheral enhancement was appreciable in only two patients while a homogeneous enhancement was observed in six. Clinical symptoms resolved completely in 14/16 patients on clinical evaluation at the third postoperative day, while the remaining two patients showed residual symptoms and signs of radicular compression. At the early MRI these two patients showed intradural nerve root enhancement. Two months later, one patient did not show the previously described nerve root enhancement and improved clinically, while the other had a positive Straight Leg Raising Sign with persistent intradural nerve root enhancement. In conclusion, no correlation between clinical course and contrast-enhancement of pseudohernia and extradural nerve root was appreciable, although intradural nerve root enhancement seems to represent a clinically relevant finding.